Figure 1.

Model states and reactions. (A) A CaMKII subunit can exist in one of six states depending on CaM binding and phosphorylation at several sites. The six states are as follows: D_uu, autoinhibited; C_u, CaM-bound, unphosphorylated; C_p, CaM-bound, phosphorylated on T286; D_pu, phosphorylated on T286; D_pp, phosphorylated on T286, T305, and T306; and D_uu, phosphorylated on T305 and T306. States D_uu and D_up are inactive; the other states have varying activity levels. (B) A schematic view of the dodecameric CaMKII holoenzyme. Association domains are shown in red, regulatory domains in blue, and kinase domains in orange. (C) Reaction diagram describing conversion between the six states of CaMKII. See the text for details.